Alzheimer's disease is a neurodegenerative disease which is pathologically characterized by formation of senile plaques and neurofibrillary tangle, along with neuronal degeneration and drop out. Alzheimer's disease causes symptoms of dementia; for example, progressive loss of memory, recognition, thinking, and judgment, and eventually leads to death.
Senile plaques deposited in the brain are mainly formed of amyloid-β peptide (Aβ), and this protein is composed of 39 to 43 amino acid residues. Aβ, which exhibits cytotoxicity, is considered to cause Alzheimer's disease (Non-Patent Document 1). Aβ secreted from cells is generally a polypeptide composed of 40 or 42 amino acid residues. In particular, Aβ composed of 42 amino acid residues is known to be deposited in the brain in an early stage with stronger aggregability, and to have strong cytotoxicity (Non-Patent Document 2). Thus, an Aβ aggregation inhibitor is expected to serve as a preventive or therapeutic drug for Alzheimer's disease.
L-[Lys-Leu-Val-Phe-Phe], which is a partial sequence of Aβ, is known to have inhibitory activity for Aβ aggregation (Non-Patent Document 3).